Cherry-blossom volcano spews forth lava and lightning

It looks like the end of the world - in fact it's only the end of Japan. This is Sakurajima volcano, on the southern tip of Kyushu, the most southerly of Japan's main islands. The nearby town does a nice tipple made from sweet potatoes. The photo makes it seem like a dangerous place, but when I visited, the only volcanic matter that landed on my head was ash. Still, serial volcano-chaser Martin Rietze was much closer in when he took this apocalyptic photo.

In Kagoshima, the town under the volcano, the residents are used to a dusting of ash. The volcano has been erupting - grumbling, really - almost constantly since 1955. In preparing, Rietze kept away from the potato booze - he had to wait more than 14 hours before he got the shot at 4:50 am. "Such things take high concentration and patience over a very long time," he says. "I was about 3 kilometres from the volcano. No special equipment was needed, but the ash rain is unhealthy and you have to protect the camera equipment."

Sakurajima used to be an island; the name means "cherry blossom island". It was lava from the last really big eruption, in 1914, that connected it to the mainland.

But why does lightning accompany the eruption? When volcanoes erupt, the ash flung out is electrically charged. Ash particles with positive charges tend to fall down, and negatively charged particles move up. When the charge separation becomes too much for the air to resist, an electrical pulse - lightning - zaps between the charged regions. Even so, the exact process is poorly understood.

This article appeared in print under the headline "Lava and lightning"